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Frontier Transportation, Inc. B23502.01 October 16, 1996 Page 7 were be collected in the boreholes drilled for the monitoring wells at 5-foot intervals commencing at a depth of 10 feet BSG. Soil samples were observed in the field for the purpose of developing lithologic logs and screened for evidence of PPCs with a PID consistent with our SOPS. Soil samples were not retained from the monitoring well ' boreholes. The final depth of the soil borings was determined by the depth at which groundwater was ' encountered. The boreholes were advanced to approximately 15 feet below the groundwater surface. The final depth of the boreholes for the groundwater monitoring wells ranged from 25.5 to 26.5 feet BSG. The monitoring wells was constructed of 2-inch diameter schedule 40 PVC casing and screened over the bottom 20 feet of the well. The perforations consisted of 0.01-inch machine slots. The well filter pack material, consisting of#2/12 Monterey pre-washed sand, was be placed in the annulus between the boring wall and the casing, from the bottom of the boring to approximately 1 foot above the top of the screen. Above the filter pack, a 1- to 1.5-foot thick bentonite seal was installed. The remainder of the well annulus was sealed with a 6-sack sand-cement, or cement grout slurry in one continuous operation from the bottom of the interval to be filled to the top. The grout was emplaced through the annulus of the boring. Monitoring well construction diagrams are presented in Appendix C. On August 27, 1996, a Twining environmental technician developed monitoring wells MW-1 through MW-3 consistent with our SOPs to remove excess sediment and to settle the filter pack. Development continued until the purged water was relatively sediment free, and measured field parameters (pH, electrical conductivity, and temperature) stabilized. 4.1.3 Level Survey: On September 11, 1996, the monitoring wells were surveyed b Y Y Delamare-Fultz Engineering to determine ground surface/wellhead elevations and locations. The survey data collected during this phase was referenced to a City of Tracy benchmark. The survey data was used to calculate groundwater gradient and flow direction consistent with Twining's SOPs. ' 4.1.4 Groundwater Sam lin Groundwater sampling of the monitoring wells was conducted on August 30, 1996. The monitoring wells were sampled consistent with procedures outlined in the SOPs. Groundwater sample analyses and analytical methods to be used for this characterization are summarized in section 4.2 Laboratory Testing Pr m. t4.1.5 Soil Cuttings, Decontamination Rinsate and Puree Water Disposition: Soil cuttings from the hand auger borings, drilled borings, monitoring well boreholes, rinsate from the decontamination of drill tools, and sampling purge water was containerized in United States Department of Transportation(DOT)-approved 55-gallon drums,labeled,and stored on site.